Abstract:

Both phenotypic plasticity and genotypic specialization can contribute to differences in physiological performance in species that are locally adapted to different environments. However, their relative contributions are expected to vary with respect to the spatial and temporal grain of environmental variation. In species that are distributed across steep elevational gradients, environmental conditions change dramatically over small spatial scales, and as a result, adaptive variation in physiological performance may be attributable to transcriptional plasticity in regulatory networks that underlie trait differences between high- and low-elevation populations. In this talk, I will discuss a series of common-garden experiments that were designed to examine the role of regulatory plasticity in evolutionary adaptation to high-elevation conditions in deer mice (Peromyscus maniculatus), the species with broadest elevational distribution of any North American mammal. Using a system-biology framework, I will discuss our efforts to integrate genomic surveys of DNA sequence polymorphism and genome-wide transcriptional profiles with functional assays of metabolic enzyme activities, cellular and tissue-level phenotypes, and measures of whole-animal performance. Highland mice exhibit greater thermogenic capacities than lowland mice under hypoxia, and this trait is associated with increased survival at high elevation. Our recent work has shown that this enhanced performance is associated with upregulation of transcriptional modules that influence several hierarchical steps in the O2 transport cascade, including tissue O2 diffusion (angiogenesis) and tissue O2 utilization (muscle fiber composition, metabolic fuel use, and cellular oxidative capacity). Most of these performance-related transcriptomic and physiological changes occur over physiological and developmental timescales, suggesting that regulatory plasticity makes important contributions to fitness- related physiological performance in highland deer mice.

About the Speaker:

Zachary Cheviron is an Assistant Professor in the Division of Biological Sciences at the University of Montana. Cheviron earned his Ph.D. from Louisiana State University in 2008. Prior to joining the faculty at the University of Montana in 2015, he held positions as a postdoctoral research fellow in the Department of Ecology and Evolutionary Biology at UCLA (2009-2010) and the School of Biological Sciences at the University of Nebraska, Lincoln (2010-2012), and as an assistant professor at the University of Illinois, Urbana-Champaign (2012-2015).

Cheviron’s research is aimed at understanding the physiological and molecular mechanisms that allow species to survive in challenging environments. He uses integrative approaches that draw on techniques from physiological ecology, population genetics and functional genomics to addresses a broad range of topics. These topics range from mechanistic studies of evolutionary adaptation and acclimatization responses to comparative analyses of the importance of environmental gradients in population divergence, speciation, and biodiversity conservation. Perhaps due to a prolonged lack of topographic relief during his childhood in central Illinois, Cheviron developed an early fascination with montane environments, and much of his current work focuses on birds and mammals that are distributed along elevational gradients in mountain ranges around the world.